This invention relates generally to screw fastenings and more particularly to a drive nut into which a mating member such as a screw can be relatively driven by striking or otherwise driving against a relatively low resistance into a locked state which cannot be readily unlocked except by turning either member in unscrewing action.
Heretofore, a conventional nut as specified by a standard specification has a cylindrical hole provided on its inner wall surface with a female screw thread to mesh with the male screw thread of a mating member such as a bolt or a screw. By causing relative screw turning movement between the nut and the mating member with their screw threads in meshed state, the nut is caused to move in its axial direction relative to the mating member thereby to effect tightening or loosening.
In the case where the length of the male screw thread of the mating member is long, the nut must be turned a great number of times relative to the mating member, and this disadvantageously requires much time before the tightened state between the two members is attained.